Radio frequency identification technology has become widely used in virtually every industry, including transportation, manufacturing, waste management, postal tracking, airline baggage reconciliation, and highway toll management. An RFID system is made up of two components, the transponder and the interrogator or reader. The essential components of a transponder are the data carrying device—generally referred to as an integrated circuit or an electronic microchip, and a coupling element—such as an antenna. A transponder that contains its own power supply, generally a battery, is know as an active tag, while a transponder that does not contain its own power supply is known as a passive tag, sticker or label. The interrogator or reader contains a radio frequency module (transmitter and receiver), a control unit and a coupling element—an antenna. Power and data exchange between the transponder and the interrogator are achieved through magnetic or electromagnetic fields.
An example of a radio frequency identification sticker is disclosed in U.S. Pat. No. 6,121,880 (Scott et al.), “Sticker Transponder for Use on Glass Surface.” This patent discloses a sticker transponder adapted to be affixed to a glass surface, such as a vehicle windshield, including a RFID transponder enabling the storage and retrieval of vehicle related data. The sticker transponder comprises a flexible circuit substrate having an antenna formed thereon and a transponder circuit disposed on the substrate and coupled to the antenna. An adhesive layer is coupled to a first surface of the flexible circuit substrate. An indicia layer is coupled to a second surface of the flexible circuit opposite from the first surface. The indicia layer comprises a space permitting indicia to be printed thereon. The antenna has a characteristic impedance defined in part by a dielectric constant of the glass surface. As a result, a proper impedance match between the antenna and the transponder circuit is achieved only when the sticker is affixed to the glass surface. The sticker transponder further comprises a release liner affixed to the adhesive layer, the release liner being selectively removable to permit the sticker transponder to be affixed to the glass surface. The transponder circuit further includes a memory having a read-only portion and a re-writable portion.
An example of a tamper indicating radio frequency identification label is disclosed in PCT Publication WO 01/71848A1 (Atherton), “A Tamper Indicating Radio Frequency Identification Label.” This publication discloses a label which may include RFID components and a tamper track coupled to the RFID components. The tamper track should be constructed from a destructible conducting path. Additionally, the tamper rack can be formed such that it is damaged when the label is tampered. In one embodiment, adhesion characteristics of the tamper track (102) are adapted to break apart the tamper track when the label is tampered, for example, by removal from an object. The RFID components may retain their RF capability and detect when the tamper track (102) has been damaged to indicate that the label has been tampered. Alternatively, the RFID capability of the RFID components may be disabled when the tamper track is damaged, indicating tampering.